1. Technical Field
The present invention relates to a technology for reading part of a code pattern uniformly arranged on a two dimensional surface and identifying a reading position on the two-dimensional surface.
2. Related Art
In these years, a technology for uniformly arranging a code pattern on a two dimensional surface, reading a symbol thereof, and identifying a position on the two dimensional surface has been proposed. For example, symbols are uniformly printed on an examination sheet printed on paper or the like in invisible ink or toner having infrared or ultraviolet absorption characteristic. When an answerer goes over the selected answer position by a scanner or the like, the selected answer is sent to a correspondence school or the like (refer to FIG. 1). The symbols can be printed invisible ink in addition to the invisible ink.
As such a code pattern, various patterns have been proposed. For example, as shown in FIG. 2A, a virtual grid is arranged, and a dot is arranged in one of four areas defined by an intersection of the grid. Thereby, four types of patterns can be expressed, and 2 bits can be expressed. The code pattern will be hereinafter refereed to as benchmark.
As shown in FIG. 2B, 1 bit is expressed by a right oblique straight lines and left oblique straight lines, which is called glyph code. As shown in FIG. 2C, information is expressed by a combination of straight line and key-shaped graphic patterns. As shown in FIG. 2D, information is expressed by ON/OFF of dots.